In addition to providing a language to be used with PLT Scheme
modules, Typed Scheme is also available as a language selection within
DrScheme. To enable this language, simply choose it in the “Choose
Language” dialog found in the “Language” menu of DrScheme. Typed
Scheme programs can then be entered in the definitions window, and
executed with the run button.

Unlike some other languages available in DrScheme, the Typed Scheme
language level does not simulate a top-level read-eval-print loop.
Therefore, only one definition of a variable is allowed and uses of
unbound variables result in errors.